FIG. 1 (Prior Art) is a cross-sectional diagram of a conventional conductive plug-type antifuse 110 as disclosed in U.S. Pat. No. 5,308,795. A first conductor 114 is disposed on an insulating underlying layer 112. First metal conductor 114 may comprise a sandwich structure of a lower barrier metal layer (for example, TiW), an aluminum layer (for example, AlSiCu), and an upper barrier layer (for example, TiW). Layer 116 is a layer of dielectric (for example, PECVD silicon dioxide). A conductive plug is disposed in an opening 118 in layer 116 and includes a conductive material 120 (for example, TiW) and a planarizing material 122 (for example, spin-on glass). Layer 124 is a layer of antifuse material (for example, a single layer of amorphous silicon). A capping layer 126 (for example, TiW or TiN) is provided on antifuse material layer 124 to prevent contamination of the antifuse layer from atoms in an overlying second metal conductor. Oxide spacers 128 are provided in order to minimize step coverage problems for the overlying second metal conductor 130.
When unprogrammed, the first conductor 114 is not coupled to the second conductor 130 through the antifuse 110. When programmed, however, antifuse 110 forms a permanent electrical connection between the first conductor 114 and the second conductor 130.
It is desired to improve such an antifuse.